Outboard motors conventionally include a propulsion unit having a power head including an internal combustion engine. The propulsion unit also includes a lower unit having a rotatably mounted propeller drivingly connected to the engine. Extended transom brackets are used to permit outboard motors to be mounted on the transoms of boat hulls of the type specifically designed for a stern drive or inboard engine. Extended transom brackets commonly support the propulsion unit in a position which is spaced a substantial distance rearwardly of the trailing edge of the bottom of the boat hull. The positioning of the propulsion unit in spaced relation rearwardly of the transom generates problems in performance and boat handling. Another common problem with extended transom brackets is that there is excessive water spray at the transom and around the lower unit. Additionally, the operator may experience torque in the steering system causing difficult steering. Another feature which is experienced as a result of mounting a propulsion unit on an extended transom bracket is that the boat may tend to porpoise.
It has been found that use of an extended transom bracket for supporting the propulsion unit rearwardly of the trailing edge of the bottom of the boat causes the water surface where it meets the gearcase to fluctuate in height. When the bow of the boat is raised either from the acceleration of the boat or as a result of movement of the boat through rough water, the lower unit or gearcase of the propulsion unit is driven deeper into the water. As more of the lower unit enters the water, there is an increase in the water resistance on the propulsion unit, and this increased resistance can cause porpoising of the boat. This increased resistance can also cause water spray from the lower unit forwardly toward the transom, and increased torque on the lower unit. This torque on the lower unit can cause steering difficulties.
On a conventional outboard motor, the portions of the lower unit or gearcase below the lower mount and above the anti-ventilation plate sometimes have forward portions including relatively broad surface areas. As the boat moves through the water, if acceleration or rough water causes these portions of the lower unit to enter the water, the relatively broad surface areas of the forward portions of the lower unit generate increased water resistance and each of the characteristics referred to above may occur.
Attention is directed to the U.S. Pat. No. 3,075,490 showing a bracket for attachment to a boat transom and for mounting a propulsion unit. The transom bracket of Lang is intended to permit the propulsion unit and the propeller to move downwardly into the water when the speed is increased in order to increase the operating efficiency of the propusion unit. The transom bracket of Lang also includes a deflection plate mounted below and rearwardly of the bottom of the boat hull. The deflection plate of Lang is wedge-shaped when viewed in plan and is intended to split the water such that it passes on either side of the motor strut.
Attention is also directed to the U.S. Pat. No. 4,449,945 issued May 22, 1984, and illustrating a transom bracket having a lower brace member rearwardly of a bottom portion of the transom and supporting opposite sides of the transom bracket.
Attention is further directed to the U.S. Pat. No. 1,827,806, issued Oct. 20, 1931; the U.S. Pat. No. 885,370, issued Apr. 21, 1908; the U.S. Pat. No. 3,768,432, issued Oct. 30, 1973; and the U.S. Pat. No. 2,713,843 issued July 26, 1955.